This invention relates generally to the use of ultra-high molecular weight polyethylene for a wear resistant surface and more particularly to the means by which such ultra-high molecular weight polyethylene can be effectively bonded to metallic backing plates.
Ultra-high molecular weight polyethylene can be produced with molecular weights from 500,000 to approximately six million, and as a result the material has excellent wear properties, including high impact strength, breaking strength, bending strength and abrasion resistance. Moveover, ultra-high molecular weight polyethylene possesses excellent anti-friction properties. In fact, when dry sliding against such metals as steel, brass or copper ultra-high molecular weight polyethylene exhibits apparent self-lubricating characteristics.
Ultra-high molecular weight polyethylene is water repellant and does not absorb water to any extent sufficient to induce swelling or other dimensional change. Thus, the exceptional qualities of ultra-high molecular weight polyethylene are maintained independently of the environmental moisture or humidity where the ultra-high molecular weight polyethylene is used.
All considered, ultra-high molecular weight polyethylene is promoted for uses where a surface is subjected to various types of abrasion, such as sliding abrasion, light impact abrasion or heavy impact abrasion.
For such uses, however, ultra-high molecular weight polyethylene has heretofore been supplied in sheet form, though of various thicknesses, with extensive instructions as to how the material might best be secured to a substrate. The mounting instructions suggest using various bolts, screws, rivets or power actuated fasteners. Such instructions generally warn that the fasteners must be relatively closely spaced in an attempt to minimize warping and shrinking inherent to the thermoplastic nature of ultra-high molecular weight polyethylene. Such mounting requirements mitigate against effective usage of such sheets on cured or intricate surfaces.
Thus, installation costs have been necessarily compounded, and attempts to bond the ultra-high molecular weight polyethylene directly to a metallic substrate, or backing plate, have been unsuccessful. First, no feasible means have heretofore been known to effect a successful bond between ultra-high molecular weight polyethylene and metal, and second, even if those two materials could be directly bonded, the co-efficients of expansion for ultra-high molecular weight polyethylene and metal are so disparate that the resultant internal stresses imposed on the polyethylene could destroy either the bond or the polyethylene sheet itself.